Today I tried making a variation of mac n cheese from scratch. I cooked a cup of twist egg noodles, drained them and lets them sit in the drainer while i made the sauce. I used mozzarella, Colby jack and straight cheddar to make a little over a cup of grated cheese. I put a 1 1/2 tbsp butter in the saucepan I used for the pasta and then added the cheese and poured in a little half 'n' half, around a half cup. The sauce looked like a decent consistency, but when i added the noodles it was sticking too much, so i added more cheese, then i realized that'd just make it more thick so i added more half 'n' half. I just accepted what i had made and bowled the noodles.
I had essentially made egg noodles with melted cheese, with garlic and basil. I've been cooking occasionally for a few months, this is my first time trying to make a pasta dish. What did i do wrong? I'm not looking for a recipe, just the basic guidelines that i obviously didn't follow when trying this out.

Make a white sauce. Easy - melt some butter then stir in the same amount of flour. Cook for a bit then whisk in some milk. Two tablespoons of butter and flour will thicken 1-2 cups of milk. This is a white sauce or Bechamel sauce

Turn off the heat and stir in shredded cheese. If you add the cheese while the pan is on the heat, the cheese will curdle. With the addition of the cheese, the Bechamel is now a Mornay sauce.

Pour the cheese sauce over the cooked pasta.

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"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan

I make make macaroni and cheese like Andy M, but I pour it into a casserole, cover it with more greated cheese and bake it for maybe a half an hour. If I have it on hand, I will cover the macaroni and cheese with bread dressing mix after toasting the mix in some melted butter. Ummm, probably not the healthiest way to go but my kids loved it.